Gear lapping machine



'om LAPPING CHINE Findlay 8, 195o Patented Oct. 25, 1932 UNITED STATES PATENT OFFICE CHARLES H. SCH'URR, OF CLEVELAND, OHO, ASSIGNOR T0 THE LEES-BRADNER COM- PANY, OF CLEVELAND, OHIO, A CORPORATION F OHIO GEAR LAIPING MACHINE Application Med May 8, 1980. Serial No. 450,827.

This invention relates to the finishing of gears by lapping or the like.

Heretofore, gears have been lapped by placing the gear to be operated upon on the pivot, causing it to mesh with a gear-shaped lap to which abrasive has been applied, and rotating either the blank or the lap to drive the other. This process has produced smoother surfaces on the gear teeth, but it has not properly eliminated the irregularities appearing thereon, such as are caused by distortion during hardening, as a projection on the face of one tooth forces the lap to bear upon the adjacent side of the succeeding tooth, and so to abrade 4a portion of the surface of this succeeding tooth as well asthe projection, thus destroying the accuracy of the face of` the succeeding tooth. Also, with two gears running in mesh, the part of the gear faces on the tangent pitch circles have true rolling contact, and so lack the sliding past each other necessary to abrade the surface at this point, but the amount of abrasion varies, increasing progressively from this point outwardly and inwardly to the tooth crest and root, respectively.

It is an object of the present invention to eliminate the disadvantages attendant to prior methods of lapping.

The invention w1ll be better understood from the description ofthe apparatus illustrated in the accompanying drawing which constitutes one embodiment thereof, and of the method which may be performed with the apparatus .which constitutes another embodiment. n

In the drawing, Figure 1 is a side elevation of the mechanism for lapping teeth of a spur gear; 4 Figure 2 is a central longitudinal sectional view thereof; and

Figures 3, 4, 5 and 6 are fragmentary dia.

grammatic views showing the action of the gear and lap.

The apparatus illustrated comprises a base 1 having adjacent its ends two upwardly extending standards 2 and 3, bearings 4 and 5 upon the standards carry a horizontal shaft 6 which supports the lap and operating mechanism, while at the top of the standards bearings 7 and 8 support a shaft 9parallel to shaft 6 which cariies a work gear 10 which is to be operated upon.

Mounted upon the shaft 6 is a gear 11 in mesh with a gear 12 iixed to the shaft 9, these gears being extremely accurate. Cylinders 13 are also keyed to the shaft 6v and bear against cylinders 14 on the work carrying shaft. These cylinders have diameters corresponding to the pitch circles of the gears 11 and 12, which, in turn, correspond to the pitch circles of the work gear 10 and of a lap 15 carried by the shaft 6, the function of the discs being to maintain the axes of the shafts accurately in alinement and properly spaced apart, and possibly, to some extent, assist in the transmission of power between the shafts, due to the frictional engagement of their surfaces.

It will be noted that the lap 15, gear 11 and discs 13 are all considerably wider than the engaging elements carried on shaft 9, so that shaft 9 may be reciprocated lengthwise, the longitudinal motion causing the surface of the lap and gear to slide axially upon each other, and so lap the metal of the gear at its pitch circle; For causing this longitudinal movement, a lever 16 is pivoted at 17 upon standard 2 and has a bifurcated end18 en aging a grooved collar 19 secured to the s aft 9. The lower end of the lever is provided with a roller 20 which travels in groove 21 in a cam 22 secured to the shaft 6.

The lap has an axially extending hub portion 23 on which is cut a worm wheel 24. A Worm 25 engages this worm wheel and is carried within a sleeve 26 keyed at 27 to shaft 6, the worm wheel being adjusted as byl wrench applied to its socketed end 28, so t the angular postion of the lap on shaft 6 may be varied as desired. The teeth on the lap aresomewhat thinner than would be those of4 a gear designed to properly mesh with base 10 when finished. The shafts are rotated by an suitable Source of power as by a belt driven Vpulley 29.

Gear teeth, particularly those which have been hardened by heat treatment, generally have some irregularities, both as to surface contour, and in spacing arrangement. This ioo . tooth C, the entire face of the tooth is spaced within the position of the theoretically correct curve, shown by the dotted line, which is pro A erly spaced from the faces of the two prece ing teeth. With teeth similar to those illustrated, the lap is caused to rotate with its teeth D and E just out of engagement with those of the blank. This is effected by adjustment of the worm 25. The operator, after inserting the Work gear in the machine and supplying abrasive, adjusts the worm to cause the teeth of the lap to gradually approach those on the work gear, and it will be seen, with the teeth of the diagram, the lap will first engage the projection on tooth A.

The shafts are rotated and the teeth of the the same down. Due to the positive drive between the shafts, one side only of the teeth of the work gear will be engaged by the lap, namely as shown in Figures 8 to 6, the face on the right hand side of the tooth. After a time, the lap will have abraded off the portion of the tooth A, shownas cross-hatched in Figure 4, and the teeth of the lap will have come into contact with the projection on tooth B. The o erator keeps advancing the position of the ap by slight amounts and abrasion now takes place on both teeth and B until these are reduced, as shown in Figure 5, at which point the lap is just starting to contact tooth C.

Slight additional feeding of the lap will cause the same to abrade all three teeth, as shown in Figure 6, in which each surface has been reduced to the theoretically correct curve, and moved slightly to the left, so that the spacing is also correct.

After the amount of material corresponding to the distance the lap has been fed is removed, no further abrasion takes place, and it is therefore impossible for the lap to remove too much material, as frequently happens With the use of apparatus heretofore employed, so that correct surfaces are assured.

Obviously when all the irregularities on one 4side of the tooth have been removed, the ear may be reversed and the process carrie to reduce the other side, either by reversing the gear blank itself or physically y reversing the direction of feeding the lap.

Alsoobviously, a plurality of laps may be employed, and these may be rlrran ed to mesh with the work gear on different pitch circles, as shown in my copending application, Serial Number 215,312, and in the event of more than one lap being emplo ed, it will probably be more convenient to eed the work gear upon its shaft rather than to adjust each of the laps. n

While the device illustrated has been described as showin a lap for operating upon the gear to be wor ed, two matlng gears may be used instead of the gear and lap, and each caused to lap the other in the same manner. Therefore, the term lap as herein used should include not only the conventional type of lap which is generall composed of a softer material than the wor but either of two gears designed to be used together. When these are being used to lap each other, either one may be considered as the work and the other considered as the lap.

While I have described the illustrated embodiment of my invention in some particu- L larity, obviously many others will readily occur to those skilled in the art to which this appertains, and I, therefore, do not limit myself to the precise details shown and described herein, but claim as my invention all embodiments, modifications and variations coming within the scope of the appended claims.

I claim:

1. Apparatus for lapping comprising two parallel shafts, means maintaining the shafts with their centers in fixed relation, a lap carried by one of said' shafts to rotate therewith, a work gear carried by the other shaft to rotate therewith, positive driving connections between the shafts, and means for feeding one of said member about its shaft.

2. Apparatus for lapping comprising two l shafts,.means maintaining the shafts with their centers in fixed relation, a lap carried by one of the shafts to rotate therewith, a

work gear carried by the other shaft to ro-- tate therewith, positive driving connections between the shafts, means for feeding one of saidv members about its shaft, and means for'reciprocating one of said shafts. 3. Apparatus for lapping com rising two shafts journalled lin stationary earings, a

`lap carried by one of said shafts, a work gear carried by the other shaft, one of said members being rigidly secured to its shaft and the other member being rotatable upon its shaft, an element rigidly secured to the last mentioned shaft, and adjustable means between the last mentioned member and said element.l

4. Apparatus for lapping gears comprising two shafts, means maintaining the shafts with their centers in fixed relation, a lap carried by one of said shafts to rotate therewith, the teeth of the lap being narrower than those. of the gear which would mesh with the gear to be lapped, a work gear carried by the other shaft to rotate therewith, positive llO ear 5 reciprocation of sai sha. t.

driving connections vbetween the shafts, means for reciprocatingy one of said shafts axially, the teeth of the 1a being as wide as those of the work us the amount of In testimony whereof I hereunto aix my signature this 24th day of April, 1930.

CHARLES H. SCHURR. 

